Method and apparatus for the dry release of a compliant ophthalmic article from a mold surface

ABSTRACT

An apparatus for releasing a molded lens from a deformable mold includes a shear ring for temporarily retaining an annular portion of the deformable mold outside a periphery of the lens and a plunger for deforming an annular section of the deformable mold within the periphery of the lens. The apparatus can be employed to release a non-hydrated hydrogel lens from a deformable mold section.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 12/541,246,filed Aug. 14, 2009, which is a divisional of application Ser. No.11/306,230, filed Dec. 20, 2005.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A “SEQUENCE LISTING”

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the releasing of a molded ophthalmiclens from a mold surface and in particular to the dry release of a lensformed of a compliant material from a mold.

2. Description of Related Art

The molding of contact lenses is known in the art and reference in thisregard is made to U.S. Pat. No. 5,466,147 the disclosure of which isincorporated by reference. Briefly stated, a contact lens generally isformed in a single use mold unit comprising a female mold section havinga concave optical surface and a male mold section having a convexoptical surface. The male and female mold sections are formed of asingle use deformable material and are complementary shaped. The moldsections are brought together to form a lens-molding cavity between thefacing convex and concave mold surfaces.

To form the lens, a quantity of lens forming material first is dispensedinto the concave optical surface of the female mold section. In thecontext of the present invention the lens forming material is a mixturefor producing a silicone-containing hydrogel lens. An appropriatemixture for making a silicone hydrogel lens is known in the art andreference is made to U.S. Pat. No. 5,260,000 the disclosure of which isincorporated herein by reference for a description of the process.

Briefly, and as disclosed in U.S. Pat. No. 5,260,000, the processinvolves preparing a monomeric mixture comprising a silicone-containingmonomer, a hydrophilic monomer and an organic diluent. This mixture ischarged into the mold and then the male mold section is seated upon thefemale mold section such that a lens forming mold cavity is formedtherebetween. The joined male and female mold sections form a singlemold unit that under goes a curing cycle to polymerize the lens materialin the mold cavity. Once the lens material is cured, the mold sectionsare separated to retrieve the cured lens.

Upon mold separation the cured lens generally adheres to the concaveoptical surface of the female mold section. The problem then is toeffect the release of the cured lens from the female mold sectionwithout damaging the lens. In most cases a dry release of the cured lenscan be accomplished by a method as disclosed US Publication No.2004/0061246.

In this respect the method as disclosed in US Publication No.2004/0061246 uses a plunger that that has an annular ridge on an endsurface. This annular ridge has a flat end face, which is pressedagainst the anterior surface of the female mold section. Since theanterior surface of the female mold section is curved (convex) the flatend face of the raised ridge has a relatively sharp edge that firstcontacts the curved anterior surface of the female mold section. Theforce exerted by the plunger against the anterior surface of the femalemold section is concentrated by this shape edge at a location radiallyoutward of the center of this surface. In most cases this application offorce will sufficiently deform the mold section so that the entire lenswill release from the mold. If the lens continues to adhere to the molda second force applied by the flat face of an axial plunger to thecenter of the non-optical surface will result in the release of thelens.

However, in the case of a silicone hydrogel lens, this has been foundnot to be the case in that the application of forces as noted above willnot cause the lens to release form the mold. The problem presented by asilicone hydrogel lens is that it is relatively compliant. For example,when fully hydrated, the lens may have a modulus of 70 gm/mm² or less.While the cured lens still attached to the female mold section is nothydrated, even in its dry state the cured lens still is so compliantthat the lens lacks sufficient rigidity to peel or release from the moldas the shape of the mold is distorted first by the flat face of theannular plunger and then by the axial plunger. Instead the siliconehydrogel lens contorts so as to conform along with the mold surface andremains adhered to the optical surface of the mold section even afterthe mold is distorted.

Accordingly, an object of the present invention is to provide animproved method and apparatus for releasing a compliant ophthalmicarticle from a concave mold surface.

Another object of the present invention to provide a method andapparatus for releasing a mold compliant ophthalmic article such as adry silicone hydrogel lens or the like from a concave optical moldsurface.

A further object is to effect the release of a mold compliant ophthalmicarticle such as a silicone hydrogel contact lens or the like from aconcave mold surface by causing a continuous peeling separation of thearticle from the mold surface. An additional object includes releasing anon-hydrated molded ophthalmic lens from a mold by peeling the lens fromthe mold from a radially spaced location to a central or axial location.

Yet another object is to effect the peeling separation of a compliantsilicone hydrogel contact lens from a concave mold surface wherein thepeeling starts at the outer edge of the lens and progresses radiallytowards the lens center.

BRIEF SUMMARY OF THE INVENTION

In the present invention, molded contact lens, preferably a compliantlens such as a silicone hydrogel contact lens, is released from thesurface of a female mold section, while the lens remains in a dry state.By a dry state, it is meant the lens is not yet hydrated after formationof the lens. The female mold section has an anterior surface thatincludes a concave optical surface portion or mold cavity from which themolded lens must be released and a posterior surface.

The release of the molded lens is accomplished by locating a circularshear ring against the anterior surface of the mold at a locationradially spaced from and surrounding the optical surface portion of themold cavity. A plunger, having a raised annular lip on an end surfacethen is pressed against the posterior surface of the mold so the mold ispressed between the shear ring and the plunger lip. The outside diameterof the raised lip is just less than the diameter of the circular shearring so the plunger exerts a force on the anterior surface of the moldalong an annulus that has a slightly smaller diameter than the diameterof the shear ring.

The edge of the shear ring pressed against the anterior surface of themold approximates a knife edge. In contrast, the surface of the raisedlip of the plunger that contacts and presses against the posteriorsurface of the mold is rounded. As the shear ring and plunger move onetowards the other and as each press against the mold, the portion of themold immediately above the raised lip begins to bulge upwardly. Theshear ring prevents the bulge from propagating radially outward so themold begins to roll radially inward over the rounded surface of the lip.This creates mechanical shear between the lens and the surface of themold cavity sufficient to cause the compliant lens to peel and releasefrom the mold surface. The peeling action begins at the periphery of thelens and as the plunger continues to press into the mold and the moldmaterial rolls over the rounded surface, there is a continuouspropagation of the peeling that progresses radially inward from theouter edge (periphery) of the lens to its center.

In another embodiment, the raised lip and its rounded surface arereplaced with a plurality of axially extending pins arranged about thelongitudinal axis of the plunger. The operative end of each pin isrounded and in one alternative embodiment the pins are mounted forrotation about the longitudinal axis of the plunger so that in effect, asurface of revolution is created comparable to the rounded surface ofthe raised lip as described above. The net result is a comparableapplication of force causing the lens to peel from the mold with thepeeling beginning at the periphery of the lens and propagating radiallyinward to the center of the lens. Thus, the peeling, or line ofseparation, initiates at a perimeter of the molded lens and propagatesradially inward.

In a still further embodiment the pins are mounted for axial movement.In this case the axial movement of the pins either with or with outrotation about the longitudinal axis of the plunger generates the forcefor peeling the lens from the mold.

After the lens is released from the mold, the lens is removed andtransported to a separate workstation for further operations. In apreferred embodiment a suction cup is employed to grab the lens andremove it from the mold. In particular the suction cup has a flared,generally conical wall formed of a compliant material. As the suctioncup picks up the lens, the compliant nature of the suction cup wallallows the suction cup to conform to the lens shape so there is agreater surface area of contact between the suction cup and the lens.The resulting increase in surface tension between the two acts to holdthe lens to the suction cup with minimal differential pressure.

Accordingly, the present invention may be characterized in one aspectthereof releasing a molded compliant hydrogel lens from a concave moldsurface of a deformable mold by deforming the mold in a manner thatcreates a shear force between the concave mold surface and the moldedlens to effect the peeling of the lens from the mold surface, whereinthe peeling starts at the outer periphery of the lens and progressesradially inwardly along the lens surface.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic exploded view of a representative mold assemblyfor forming a silicone hydrogel lens or other ophthalmic article;

FIG. 2 is a cross-sectional view of the mold assembly in a nestedposition;

FIG. 3 is a schematic view of an anterior section of the mold assemblyshowing the molded lens in the mold cavity;

FIG. 4 is a cross-sectional view of the release apparatus prior to thecapturing of the anterior mold section;

FIG. 5 is a view similar to FIG. 4 only showing the apparatus after thelens has been released form the mold cavity;

FIGS. 6-8 are views on an enlarged scale showing a portion showing aportion of the apparatus at various stages in the process for separatingthe molded lens from the mold cavity;

FIG. 9 is a perspective view showing another arrangement for effectingthe release of the lens form the mold surface; and

FIGS. 10 and 11 show an arrangement for plucking a molded lens from themold after the molded lens is released from the mold surface.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, FIGS. 1 and 2 show a mold assembly 10 as maybe used to make a silicone hydrogel contact lens or the like. The moldassembly 10 includes an anterior mold section 12 and a posterior moldsection 14. The mold sections 12, 14 are individually made from aplastic resin by injection molding; at least the anterior mold section12 is deformable.

The anterior mold section 12 includes a mold cavity 16 including aconcave optical surface 18 that forms the convex anterior surface 20 ofa molded lens 22. The anterior mold section 12 further includes agenerally convex, non-optical surface 24 (FIG. 2), a land 19 thatsurrounds the mold cavity 16 and an annular wall 26 that extendsgenerally perpendicular from about the periphery of the land.

The posterior mold section 14 includes a convex optical surface 28 (bestseen in FIG. 2) that forms the concave posterior surface 30 of themolded lens. The posterior mold section 14 has a concave non-opticalsurface 32 located opposite the convex optical surface 28 and an annularwall 33 that defines the outer periphery of the posterior mold section.

In an assembled position as shown in FIG. 2 the mold sections 12, 14nest together with the anterior section 12 being disposed within theposterior section 14. In this position, a mold cavity is formed betweenthe optical surfaces 18, 28 that receives and molds a curable materialfor making the molded lens 22.

To form a molded lens, a curable liquid is cast into the mold cavity 16in the anterior mold section 12. Then the anterior and posterior moldsections 12, 14 are nested as shown in FIG. 2 so the liquid conforms tothe shape of the mold cavity formed between the mold sections. After atime sufficient to allow the liquid to polymerize, the mold sections 12,14 are separated leaving the molded lens 22 in the mold cavity 16 of theanterior mold section 12 as shown in FIG. 3.

Separation of the mold sections 12, 14 leaves the molded lens 22 adheredto the optical surface 18 of the anterior mold section 12. The problemnow is to effect the separation of the lens 22 from the optical moldsurface 18 without doing damage to the lens.

One prior art method for separating the lens from the mold is disclosedin US Publication No. US 2004/0061246. As described in this publication,the lens is released from the mold surface by applying a force to thegenerally convex, non-optical surface of the anterior mold section. Thisdistorts the optical surface opposite the non-optical surface so as toeffect a separation of the lens from the mold surface.

While this prior art method is effective for most types of moldedcontact lenses, it is not effective in cases where the molded lens ishighly compliant. As noted above, a highly compliant lens tends todeform with the optical surface of the mold so there is no relativeshear developed between the lens and the optical surface sufficient toeffect the separation of the lens. Accordingly, the method as disclosedin US 2004/0061246 is ineffective for separating a compliant lens and inparticular a silicone hydrogel lens, from the anterior mold section.

In accordance with the present invention, FIG. 4 shows that the lensrelease apparatus includes a female section 34 having a circular recess36 configured to receive therein the anterior mold section 12 with theattached molded lens 22. The female section 34 includes an annular shearring, such as knife edge 38 that extends into the recess 36. Thediameter of the shear ring, such as knife edge 38, is slightly greaterthan the diameter of the mold cavity 16 for purposes set outhereinbelow. It is contemplated the shear ring 38 can be formed by anacute or obtuse transition between two faces or facets. Therefore, whilethe knife edge 38 configuration of the shear ring is shown with an acuteincluded angle, the knife edge can be defined by an included anglegreater than an acute angle. It is further contemplated that the shearring 38 can include a radius, however it is believed advantageous toemploy a relatively abrupt edge, such as the knife edge, andparticularly along the radially inner face of the shear ring. That is,beyond the radially innermost contact between the shear ring 38 and theupper surface of the anterior mold section 12, the contact configurationis not believed to be critical.

The release apparatus also includes male section comprising an axiallymovable plunger 40. The longitudinal axis of the plunger 40 is alignedwith the axis of the female section 34 so the plunger can move axiallyinto the circular recess 36. Located on an end face of the plunger 40 isan annular raised lip 42. The raised lip 42 has a radial cross sectiondefined by a rounded surface 44 and the diameter of the annular raisedlip is less than the diameter of the shear ring or knife edge 38 so theentire lip lies within the annulus of the knife edge. It is understoodan interchangeable center pin may be utilized for increased robustnessand versatility of dry release with different mold/monomer families.

The outside diameter of the plunger 40 is slightly smaller than theinside diameter of the anterior mold section 12. This allows the plunger40 to receive the anterior mold section 12 over the end face of theplunger so the raised lip 42 rests against the convex posterior surface24 of the mold section 12 in a position that is generally concentricwith the molded lens 22. When the mold section 12 is positioned over theend of the plunger 40, the plunger is moved axially to introduce theanterior mold section 12 into the circular recess 36 of the femalesection 34. The plunger 40 continues to push the anterior mold section12 into the recess 36 until the annular knife edge 38 presses againstthe land 19 in a position that is generally concentric with the moldedlens 22.

When the anterior mold section 12 is firmly seated within the recess 36and against the shear ring 38 any further travel of the plunger 40towards the knife edge acts to distort the anterior mold section 12 soas to effect the separation of the molded lens 22 from the opticalsurface 18 of the mold section as shown in FIG. 5. In this respect FIGS.6-8 show in schematic fashion the sequence whereby the molded lens 22separates from the optical surface 18 of the mold section 12.

FIG. 6 shows the rounded surface 44 of the annular raised lip 42 as thelip starts to press against the convex, non-optical surface 24 of theanterior mold section 12 and to move the land 19 of the mold sectionagainst the annular knife edge configuration of the shear ring 38. Asthe plunger 40 continues to move, the rounded surface 44 begins to pressinto the non-optical surface 24 and causes the mold section 12 todistort an annulus that is just radially inward of the outer edge orperiphery of the lens 22 as shown in FIG. 7.

The knife edge 38 likewise presses into the land 19 along an annulusthat is just radially outward of the outer edge or periphery of the lens22. The two members pressing against opposite sides of the anterior moldsection 12 and the resulting distortion of the mold cavity producesshear between the optical surface 18 of the mold cavity and the convexsurface 20 of the molded lens 22 sufficient to effect a separation ofthe outer edge of the lens from the optical surface as shown at 46 inFIG. 7.

FIG. 8 shows that as the plunger 40 continues to move, the plungercauses the mold cavity to bulge upwardly. The shear ring as a knife edge38 pressing against the land 19 prevents the bulge from propagatingoutwardly in a radial direction so the bulge is confined to the annulusdefined by the knife edge. Accordingly, as the plunger 40 continues tomove, the non-optical surface 28 rolls over up and over the raised lip42. The rounded surface 44 of the raised lip 42 facilitates this rollingaction. The result is that the shear created between the optical surface18 and the convex surface 20 of the molded lens 22 continuouslyprogresses inward from the outer edge of the lens so the separation 46that begins at the outer periphery of the molded lens propagatesinwardly so the convex lens 20 peels from the optical surface 18. Theanterior mold section 12 takes a permanent set when distorted allowingthe easy removal of the molded lens 22 from the mold.

The rounded surface 44 of the raised lip 42 is important for thedevelopment of a shear force sufficient to effect the separation of thelens 22 from the mold cavity (mold section 12) and for the correctpropagation of the shear force. In this respect the rounded surface ofthe raised lip 42 allows the mold material, such as lens 22, to roll upand over the raised lip so there is a smooth continuous propagation ofthe shear force radially inward from the outer edge of the molded lens.

The shear ring 38 can contact the anterior mold 12 outside the peripheryof the molded lens 22, either along the convex portion of the anteriormold as seen in FIG. 5, or along the land area 19 of the anterior mold,as shown in FIGS. 6-8. The critical aspects include the contact of theshear ring 38 with the anterior mold 12 radially outward of theperiphery of the molded lens 22 and contact of the raised lip 42radially inward of the shear ring.

As described hereinabove, the raised lip 42 and rounded surface is acontinuous member that presents an unbroken surface (the rounded surface44) for pressing against the convex, non-optical surface 24 of theanterior mold section 12. In the embodiment as shown in FIG. 9, theplunger 24′ includes an outer shell 48 and a rotatable core 50. The endface of the core 50 has a plurality of rounded projections 52. When thecore 50 is rotated about the longitudinal axis of the plunger 24′, asurface of revolution is created that approximates the continuousrounded surface 44 of the raised lip 42. Accordingly, advancing therotating plunger core 50 against the convex, non-optical surface 28 ofthe anterior mold section 12 mimics the action of the raised lip 42. Inaddition the rotation of the rounded projections against the convex,non-optical surface of the mold section “ripples” the mold cavity sopeeling occurs at multiple points about the perimeter of the molded lens22. The rippling adds another component of force that aids in theseparation of the molded lens 22 from the optical surface of the mold.

After the molded lens 22 is separated from the optical surface of themold section 12, a picker can be used to pluck the lens from the mold.In this respect, FIG. 10 shows a picker 54 including a generally conicalsuction cup 56. A line 58 that includes a flexible portion connects thesuction cup to a suction pump (not shown).

In operation, the picker 54 moves over the anterior mold section 12. Asnoted above the mold section 12 takes a permanent set after distortionby the plunger 40 and the shear ring 38 so the molded lens 22, nowseparated from the concave optical surface, sits in the distorted cavity16 of the anterior mold section 12. The picker 54 is moved over the moldsection 12 as shown in FIG. 10 and is lowered close to or against themold section over the molded lens 22.

When suction is applied, the lens 22 is picked from the mold. Both thesuction cup 56 and the molded lens 22 are compliant so the lens invertsas shown in FIG. 11 and the two members generally conform one to theother. This conformity increases the surface area of contact between thesuction cup 56 and the molded lens 22 so a surface tension is createdbetween the conical interior surface 60 of the picker 54 and the moldedlens. This surface tension allows the lens 22 to remain captured by thepicker even if suction is stopped so there is less likelihood of damageto the lens during the removal. After removal from the mold, the lens 22either is manually removed from the picker 54 or an air pulse appliedthrough the line 58 to expel the molded lens.

It is also understood the either or both of the lip 42 and the knifeedge 38 can be continuous or substantially continuous surface. That is,one or both of the lip 42 and the shear ring such as knife edge 38 canhave a discontinuity and still effect peeling of the lens 22 from themold surface 18.

Accordingly, having the described the invention in detail it should beappreciated that the present invention accomplishes its intended objectsin providing an improved method and apparatus for releasing a compliantophthalmic article from a concave mold surface and in particular amethod and apparatus for releasing a molded compliant ophthalmic articlesuch as a silicone hydrogel lens or the like from a concave optical moldsurface.

The method and apparatus of the present invention provides for therelease of a molded compliant ophthalmic article such as a siliconehydrogel contact lens or the like from a concave mold surface by causinga peeling separation of the article from the mold surface, wherein thepeeling separation starts at the outer edge of the lens and progressesradially towards the lens center.

Although the invention has been described with respect to certainexemplary embodiments, other modifications will be readily apparent toskilled practitioners of this art in accordance with the overallteaching of this invention. For example, although the invention isprimarily directed to improvements in contact lenses, other ophthalmicbiomedical optics could also benefit from the invention.

1. A method for releasing an ophthalmic molded lens from a mold cavityof a deformable mold, the deformable mold having an anterior moldingsurface and an opposite curved posterior surface, the method comprising:a) distorting the anterior molding surface by i) pressing against thecurved posterior surface along a first annulus; and ii) pressing againstthe anterior molding surface along a second annulus comprising a shearring; b) the first and second annuli being generally concentric with themolded lens with the first annulus being within a perimeter of themolded lens and the second annulus being radially spaced from theperimeter of the molded lens; and c) the distorting of the moldingsurface creating sufficient shear between the molded lens and themolding surface to effect a peeling of the molded lens from the moldingsurface.
 2. The method of claim 1, wherein the peeling progressesradially inward from the perimeter of the molded lens.
 3. The method ofclaim 1, wherein pressing against the curved posterior surface iscontinuous along the first annulus.
 4. The method of claim 1, furthercomprising forming the first annulus of a rounded surface.
 5. The methodof claim 1, wherein pressing against the curved posterior surface isintermittent along the first annulus.
 6. The method of claim 1, whereinpressing against the anterior molding surface is continuous along thesecond annulus.
 7. The method of claim 1, wherein pressing against theanterior molding surface is intermittent along the second annulus. 8.The method of claim 1, further comprising forming the shear ring toinclude a knife edge.
 9. The method of claim 8, further comprisingforming the knife edge from facets intersecting at an acute includedangle.
 10. The method of claim 8, further comprising forming the knifeedge from facets intersecting at an obtuse included angle.
 11. Themethod of claim 1, further comprising hydrating the molded lens afterpeeling of the molded lens from the molding surface.
 12. The method ofclaim 1, further comprising releasing an ophthalmic molded lens having ahydrated modulus less than 70 gm/mm².